I can and do shoot 32 S&W long through my 1882 and 1929 without issue, I just don't reuse the brass.
They would have already been removed from service by the later dates. The Swiss didn't reissue small arms generally, they would keep them or put them into storage with a new production firearm being made for the next batch of troops. Notable exemptions being the 96/11 rifles when they took back the 1889/96 and converted them to GP-11. It is also why most the Swiss arms are in such good shape, generally only being issued to one soldier for a limited amount of time.
Personally I think they kept the black powder loading to keep their black powder manufactures in business. The Swiss were very influenced by civilian shooting (including black powder shooters) and would keep not as good tactical firearms due to this, such as keeping the G1911 when the military felt the K1911 was sufficient for military usage and handier. The civilian shooters preferred the G11s due to the longer sight radius and because of that increased target accuracy.
The US had similar issues with the Krags and 1903 Springfields, needlessly complex sights for a military firearm, yet the marksmen were insistent on it.